In surge flow systems it is desirable to provide means whereby an output port can be isolated from an input port in order to control the flow of fluids in a system. This flow control has heretofore been achieved through the use of a maximum pressure selector device.
Typically, maximum pressure selector devices have been constructed to comprise a valve ball enclosed in a chamber and located between two opposing input ports. The application of a higher pressure signal at either of the ends of the chamber drives the ball to the opposite seat and thereby cuts off the resulting lower pressure signal from the other input port. This valve action controls flow through an intermediately disposed output port.
In typical maximum pressure selector devices, the mid-position force on the ball is relatively small enabling the ball to be jammed by dirt accumulating in the space between the valve ball and the chamber wall. Excessive surge flow problems resulting from such jamming can disturb the operation of critical devices operating from a common regulated supply pressure. Additionally, some prior art devices have not been as quickly responsive to control pressures as desired for certain applications.